9.25 SCT or Refractor for imaging?

[Adaaam75]

Guys and girls,
 
I am building my shed observatory this summer ready for the winter and currently have a SW 130 on an EQ2 mount which I love because it literally opened my eyes up to the cosmos and at £200 cannot be faulted for the results I have gotten to date. However, it is my intention to upgrade my scope to something in the area of a budget of £1600 (limit) and my decision up until recently was a Celesteon 8" SCT / 9.25" SCT on the AVX/CGEM depending on discounts and deals etc with a view to enjoy the scope and really learn the sky before slowly investing in tracking cameras/Finderscopes/CCD's/focal reducers/filter wheels etc. My main aim is to enjoy visual targets but also have a set up that will allow respectable images to be produced including DSO's. Now i'm not looking to challenge Damian Peach et al however I do understand with time, practice and patience i will be able to be proud of my work.
So my dream Celestron set up on a pier in my obs was the goal, right up until I started digging around on this fantastic site and discovered the capabilities of refractors. Now I am not ashamed to admit I disregarded refractors after the advice from experts stating SCT are better performers for DSO targets than refractors and can handle solar system objects too whereas refractors are awesome  for planets etc but fall short on DSO’s.  
I understand speed and focal lengths and I get light gathering but having seen the images on this site that have been produced from refractors I am now finding myself looking at prices for 80/100/120 and even 150mm refractors too. I’ll give you some examples....
SkyWatcher Evostar-150 EQ6 PRO SynScan £1500

Celestron Advanced VX 9.25 Schmidt Cass  £1700

Celestron Advanced VX 8” EdgeHD £1600

Celestron CGEM 9.25 varies in price but can drop to £1700

SW EQUINOX-80 ED PRO + NEQ6 PRO SynScan £1500

Are there some obvious questions I need to ask myself that I am missing or is this simply down to a matter of preference? Is there a SCT v Refractor rivalry going on similar to skiers and snowboarders (I board!!!) or are there more technical answer session that I am looking for that have so far gone above my head?
This site is clearly a platform for help and advice so please consider me a newbie (nebula as my status suggests!) and bestow wisdom upon thee.
I’d like to know the pros and cons of the variety of scopes above and the benefits of say the Equinox 80ED over the almost double Evostar 150? And why I should consider these over a SCT. Lots of questions I know but your knowledge and advice could help avoid unknown disappointment and assist me in getting the right “dream scope”. Obviously my pier woll be built after the scope is purchased!

Thanks for listening guys, this site truly is remarkable and only as good as the members.

 

[Marky1973]

Hi Adaaam.

As ever, I start with the caveat that I am no expert, and am largely repeating what I have read on these pages but, in all honesty, your decision is going to come down to what you want to see and image through the scope. I don't think there is such a rivalry between Frac and SCT owners - both types of scopes have the advantages and disadvantages depending on your plan.

I use an ED80 refractor for imaging and it is a great scope for fairly widefield shots of DSOs, clusters, nebula etc etc. It even manages to image the planets - certainly Jupiter and Saturn are manageable (with barlows) and is very good on the Moon. If you want to get "closer" to the planets, then an SCT, like the 9.25, will help you do that and will be much better at resolving the planets than my ED80. However, with its much longer focal length, it's field of view is much smaller, so widefield shots are out and many of the larger DSOs, such as Andromeda, will not be covered by it - not so much of a problem for visual when you want to get up close and personal, but can be a problem for imaging, where you end up having to produce mosaics.

With a longer focal length, the SCT will also be more of a challenge to guide; and you will want to get into guiding once you get into imaging, so you can get longer and longer exposure of your targets. A shorter, widefield scope will be easier to manage when guiding, certainly when starting out to get used to the idea.

But people do use all sorts of scopes for imaging and produce some stunning results - so this isn't about putting you off, but just to suggest you think carefully about what it is you are most interested in viewing and imaging and get the scope that is better for your main preferences.

And don't discount Reflectors either. The PDS version of your SW130 is also a very popular imaging scope.

In an ideal world, I would have a collection of scopes/imaging rigs to play with - starting from a modded DSLR for widefield imaging, alongside the ED80 for larger DSOs and narrowband imaging of nebula, with perhaps a 200PDS for smaller DSOs and a C9.25 for planetary work....but I don't quite have the cash.....yet! Essentially, there is no "one" scope that will do everything for you, so you need to think about what you want that scope to do.

Check out this field of view calculator and you can compare a number of targets with different cameras/scopes/eyepieces to get an idea of what you will see and that might help you decide.

http://astronomy.tools/calculators/field_of_view/

Good luck!

[swag72]

Interesting reading your posts and the 'experts' views that SCT's are better for DSO's than refractors and refractors fall short on DSO's. 

I have used and SCT and refractor for DSO imaging. THE biggest difference is the field of view you are going to get. Spend a lot of time of the FOV calculators out there such as this one - put in all combos that you are looking at. What you will find is that the refractor will give you a much wider field of view and so you will be able to fit larger DSO's onto your chip. The SCT will give you a narrow field of view and you will see just how small it is in comparison to the refractor.

There is a caveat to all of this ............. I am ONLY considering DSO imaging.

Imaging is all about the mount and end up under-mounted at your peril. The refractor will be much easier to use as it is less focal length and will place less stresses on your mount. It will be lighter, shorter focal length, less prone to breeze / wind issues. There's a reason why many people use them. I haven't even touched on the speed of the refractor (much quicker than the SCT) and so you will be able to gather data quicker as well. The SCT is tough going for imaging in my experience..... it's slow, it's unforgiving of ANY errors at all and it's certainly not something I'd want to I'd want to have started imaging with.

If you've not already done so, get hold of the book 'Making Every Photon Count' available from the FLO website in the book section. It's something of an imaging bible and should be read and understood before you spend a penny.

Of course if you go for a refractor then you are going to limit your planetary imaging .......... but that's why people have more than one scope, because there isn't one that does it all sadly.

I hope that helps.

[Mr Spock]

I don't know what you've been reading but you have things a little mixed up.

Imaging DSO - to start a short focal length refractor on a very good mount is the best. Longer focal lengths require a better mount and lots of skill.

Imaging planets - an SCT, C9.25 or if you can, C14. These tend to be the most popular but a good long focal length Newt will be good too.

Visual DSO - a large Dob. The bigger the better - over 12" or more.

Visual  planets - an SCT (C9.25 is perfect) or a Newt of around 10" are best. Around 9-10" makes the most of seeing conditions. On better nights larger apertures will be better but those nights are rare.

Refractors tend to have better contrast on planets but you are never going to be able to afford one with the same resolution as an SCT or Newt. As my colleague once said 'You canna change the laws of physics'

[PhotoGav]

Much good advice posted already. Your question is "SCT or Refractor" for imaging? I would have to say, in general, a refractor is best for imaging DSO and an SCT for planetary. You can do the other with each, but at a compromise. Remember, the best scope is the one you enjoy using! Really you need a selection of scopes for all the different targets you want to view and image. I have a 71mm refractor, an 80mm refractor and an 8" SCT. I also have a very long shopping list of what I want to add to my arsenal! Top of that, after the observatory, is a long refractor, but that's because I like DSO imaging.

As Sara says, make sure you invest in a really good mount, HEQ5 at minimum.

For ease of learning to image DSOs, you can't go too wrong with a skywatcher 80ed and reducer to start you off. A 9.25" SCT would be a fine scope for planetary work, but I wouldn't start your DSO imaging journey with that, keep it for when you are more experienced.

Good luck and clear skies!

[Physopto]

I started with a 12" Meade SCT. Nice optics but soon found that I was serverely limited in what I could see.  At that time I was doing purely visual. There are only so many planets and not all visible at the same time.DSOs then became more interesting. BUT you cannot get a heck of a lot of them "all " in the view afforded by a SCT. The field of view is just too restricted. So I then changed and bought a refractor. I got a 132mm f7 triplet scope thinking I had it all sussed, not so, over time I have found I am still restricted in field of view. The more interesting, to me, Horsehead Nebula and surrounding area needed a smaller scope to get it all in. So I am now setting up a smaller scope, 85mm to try and capture that elusive extra field of view!

Therefore you could say I am regressing so to speak. I will keep the 132mm and play with my new toy as well to see what I can get. I miss the SCTs narrow field of view at times and much higher magnification, but the wider field afforded by the refractor is more useful to me. There are more targets to choose from as I have now moved on into imaging. I still do some observing but not much, I have found that imaging suites me better, it "floats my boat" so to speak!

The point of all this, is that you never know exactly what you really want,  until you actually have tried and done it. Then, even then, tastes can and often do change. There is no " one size fits all" solution to astronomy. It is many times,  a try it and see hobby. All this mixed in with the inevitable cost to the bank account. 

All  good fun in the end though, so enjoy the ride!

Derek

[michael.h.f.wilkinson]

49 minutes ago, Physopto said:

I started with a 12" Meade SCT. Nice optics but soon found that I was serverely limited in what I could see.  At that time I was doing purely visual. There are only so many planets and not all visible at the same time.DSOs then became more interesting. BUT you cannot get a heck of a lot of them "all " in the view afforded by a SCT. The field of view is just too restricted. So I then changed and bought a refractor. I got a 132mm f7 triplet scope thinking I had it all sussed, not so, over time I have found I am still restricted in field of view. The more interesting, to me, Horsehead Nebula and surrounding area needed a smaller scope to get it all in. So I am now setting up a smaller scope, 85mm to try and capture that elusive extra field of view!

Therefore you could say I am regressing so to speak. I will keep the 132mm and play with my new toy as well to see what I can get. I miss the SCTs narrow field of view at times and much higher magnification, but the wider field afforded by the refractor is more useful to me. There are more targets to choose from as I have now moved on into imaging. I still do some observing but not much, I have found that imaging suites me better, it "floats my boat" so to speak!

The point of all this, is that you never know exactly what you really want,  until you actually have tried and done it. Then, even then, tastes can and often do change. There is no " one size fits all" solution to astronomy. It is many times,  a try it and see hobby. All this mixed in with the inevitable cost to the bank account. 

All  good fun in the end though, so enjoy the ride!

Derek

I have bagged over 900 DSOs including 600 galaxies with an 8" SCT (so far), and don't understand why a 12" couldn't find many more than that. Most DSOs by far fit easily in the FOV of an SCT. A handful require wider fields.

 

[ollypenrice]

The SCT for deep sky imaging is, as others have said, a difficult choice. If you don't intend to go for monochrome CCD then don't go for an SCT for deep sky imaging. DSLR pixels are too small for the long focal length and will require you to have very remarkable seeing and very remarkable guiding if they are going to translate into real details in a picture. If you fail to find the seeing or reach the guiding precision required then the only thing your long focal length will do is reduce your field of view. A shorter FL refractor will give you the same detail and a wider filed of view.

I would never recommend an SCT as a first deep sky imaging instrument.

Olly

[Physopto]

1 hour ago, michael.h.f.wilkinson said:

I have bagged over 900 DSOs including 600 galaxies with an 8" SCT (so far), and don't understand why a 12" couldn't find many more than that. Most DSOs by far fit easily in the FOV of an SCT. A handful require wider fields.

 

I was at that time very new to astronomy. I also live in a very light polluted environment and never was able to see any DSOs because of the pollution. The scope was also far too big and heavy to transport to either Kielder or Galloway. I am like most, still learning, it is long process. Having moved over to imaging I am also much happier, just a personal thing.

 

Derek

[alacant]

I'm sure the mirror guys are gonna laugh at me but my 6" f5 Petzval is great for dso stuff. No spikes on stars either. Having had a go with that and an awful time with a 250mm skywatcer, I'd go for the big refractor. Bresser have on on offer under €400. Nice flat field. ---takes cover...

[michael.h.f.wilkinson]

20 minutes ago, alacant said:

I'm sure the mirror guys are gonna laugh at me but my 6" f5 Petzval is great for dso stuff. No spikes on stars either. Having had a go with that and an awful time with a 250mm skywatcer, I'd go for the big refractor. Bresser have on on offer under €400. Nice flat field. ---takes cover...

Why should we laugh at such a scope? Nice aperture, flat field, obstruction free. Should work a treat on DSO imaging for a huge range of targets. SCTs and the like are more suitable for planetary imaging, and for very compact DSOs (planetary nebulae, many galaxies), and then only really with a focal reducer.

 

[Owmuchonomy]

All the above.  Decide what your image quality expectations are and read the book mentioned by Sara before you spend any money.  There is an awful lot to go in the mix.  I imaged DSOs with a 4" supposedly high quality triplet for a couple of years and was bitterly disappointed with it's (my) performance.  On the other hand it took an amazing image of Mars at opposition in 2014.  I also have a 9.25" SCT and my favourite image taken with that remains the 2014 SN in M82.  Its all about what you want to get from it (in my view).

[Adaaam75]

11 hours ago, Marky1973 said:

Hi Adaaam.

As ever, I start with the caveat that I am no expert, and am largely repeating what I have read on these pages but, in all honesty, your decision is going to come down to what you want to see and image through the scope. I don't think there is such a rivalry between Frac and SCT owners - both types of scopes have the advantages and disadvantages depending on your plan.

I use an ED80 refractor for imaging and it is a great scope for fairly widefield shots of DSOs, clusters, nebula etc etc. It even manages to image the planets - certainly Jupiter and Saturn are manageable (with barlows) and is very good on the Moon. If you want to get "closer" to the planets, then an SCT, like the 9.25, will help you do that and will be much better at resolving the planets than my ED80. However, with its much longer focal length, it's field of view is much smaller, so widefield shots are out and many of the larger DSOs, such as Andromeda, will not be covered by it - not so much of a problem for visual when you want to get up close and personal, but can be a problem for imaging, where you end up having to produce mosaics.

With a longer focal length, the SCT will also be more of a challenge to guide; and you will want to get into guiding once you get into imaging, so you can get longer and longer exposure of your targets. A shorter, widefield scope will be easier to manage when guiding, certainly when starting out to get used to the idea.

But people do use all sorts of scopes for imaging and produce some stunning results - so this isn't about putting you off, but just to suggest you think carefully about what it is you are most interested in viewing and imaging and get the scope that is better for your main preferences.

And don't discount Reflectors either. The PDS version of your SW130 is also a very popular imaging scope.

In an ideal world, I would have a collection of scopes/imaging rigs to play with - starting from a modded DSLR for widefield imaging, alongside the ED80 for larger DSOs and narrowband imaging of nebula, with perhaps a 200PDS for smaller DSOs and a C9.25 for planetary work....but I don't quite have the cash.....yet! Essentially, there is no "one" scope that will do everything for you, so you need to think about what you want that scope to do.

Check out this field of view calculator and you can compare a number of targets with different cameras/scopes/eyepieces to get an idea of what you will see and that might help you decide.

http://astronomy.tools/calculators/field_of_view/

Good luck!

Marky,

 

I really appreciate your time and the information you have provided. Before I posted my question, your amazing website was one of the sites I actually visited and your images especially the Whirlpool Galaxy (exquisite!) were a catalyst to my conundrums! Your advice is extremely useful and had helped me understand the searching for the ultimate scope is futile as there are specific scopes for specific tasks. The website address you posted at the end of your reply has also brought into visual context what I am dealing with and helped me understand the expectations and capabilities of various set ups. I hadn't considered the issues of stacking DSO's as I assumed any scope/CCD lens would capture the entire image in one frame. What scope/set up did you image the Whirlpool Galaxy with?

[Marky1973]

Thanks for the kind words - not sure the website is "amazing" as you'll find a lot more talented and experienced people out there than me, but I appreciate the words!

Be careful not to confuse the issue with stacking and what, I believe, we are referring to as mosaics - when imaging a DSO we take lots of photos and then stack them using software before we process them into a final, stunning (hopefully) image. When I referenced the mosaic, that was where you can't fit the whole image on your camera sensor and need to take a "matrix" of images to cover the whole target and then put them together after processing, much like a panorama - what you can and can't get in the frame will depend on your camera and scope, which is where that Field of View calculator can be very helpful!

The whirpool picture was taken IIRC with my modified Canon 100D attached to the skywatcher ED80 on an NEQ6 mount, and guided exposures - about 3 hours of data all told. I wanted to go back and try it with my mono Atik camera, but just haven't had the chance this year - just counting down the days to the nights drawing in..

Just to repeat what everyone has said, you will never find the perfect scope for everything, so you do really need to think carefully about what your interest is - that will point you in the direction of the best scope to start off with.

[Adaaam75]

12 hours ago, swag72 said:

Interesting reading your posts and the 'experts' views that SCT's are better for DSO's than refractors and refractors fall short on DSO's. 

I have used and SCT and refractor for DSO imaging. THE biggest difference is the field of view you are going to get. Spend a lot of time of the FOV calculators out there such as this one - put in all combos that you are looking at. What you will find is that the refractor will give you a much wider field of view and so you will be able to fit larger DSO's onto your chip. The SCT will give you a narrow field of view and you will see just how small it is in comparison to the refractor.

There is a caveat to all of this ............. I am ONLY considering DSO imaging.

Imaging is all about the mount and end up under-mounted at your peril. The refractor will be much easier to use as it is less focal length and will place less stresses on your mount. It will be lighter, shorter focal length, less prone to breeze / wind issues. There's a reason why many people use them. I haven't even touched on the speed of the refractor (much quicker than the SCT) and so you will be able to gather data quicker as well. The SCT is tough going for imaging in my experience..... it's slow, it's unforgiving of ANY errors at all and it's certainly not something I'd want to I'd want to have started imaging with.

If you've not already done so, get hold of the book 'Making Every Photon Count' available from the FLO website in the book section. It's something of an imaging bible and should be read and understood before you spend a penny.

Of course if you go for a refractor then you are going to limit your planetary imaging .......... but that's why people have more than one scope, because there isn't one that does it all sadly.

I hope that helps.

Swag72,

Your passion for Refractors is exactly what i need to help make my decisions. I need to consider the balance of what appears to be jumping in at the deep end of DSO imaging with a SCT vs overall results of a refractor. Having seen the quality of the images on this forum and also Marky's site I have  certainly under estimated the capabilities and reduced difficulty of imaging and processing of a refractor compared to the SCT.

It does appear that I have been short sighted and wanted the mythical all rounder without understanding each types capabilities. I have seen the book you recommended mentioned and highly thought of elsewhere so will be purchasing it within the next couple of days, it appears to be as rare as a bible too as Amazon/eBay etc don't have it anywhere.

Am I correct in saying that balancing Refractors can be more challenging when imaging but then i suppose due to their speed the imaging times are reduced compared to SCT's so long exposures wont be as common?

 

Thanks for your time in answering my queries!

 

Clear skies

 

[Marky1973]

As Sara mentioned, the book is only available through FLO - from what I am aware

https://www.firstlightoptics.com/books/making-every-photon-count-steve-richards.html

 

[Adaaam75]

11 hours ago, Mr Spock said:

I don't know what you've been reading but you have things a little mixed up.

Imaging DSO - to start a short focal length refractor on a very good mount is the best. Longer focal lengths require a better mount and lots of skill.

Imaging planets - an SCT, C9.25 or if you can, C14. These tend to be the most popular but a good long focal length Newt will be good too.

Visual DSO - a large Dob. The bigger the better - over 12" or more.

Visual  planets - an SCT (C9.25 is perfect) or a Newt of around 10" are best. Around 9-10" makes the most of seeing conditions. On better nights larger apertures will be better but those nights are rare.

Refractors tend to have better contrast on planets but you are never going to be able to afford one with the same resolution as an SCT or Newt. As my colleague once said 'You canna change the laws of physics'

Mr Spock,

Thanks for the frank and to the point summaries. As has already been suggested I need a decent Refractor, a C14 SCT and a large Dob. Hmmmmm maybe when a retire!!!

Discounting a Dob for now I am getting the feeling that an 8/9.25 SCT on a suitable mount capable of carrying the weight of this and future imaging equipment would be better for me at this stage prior to entering the realm of imaging of DSO's. I'm beginning to understand that I need to be clear on what my short, medium and long term goals are in conjunction with budgets.

[Adaaam75]

11 hours ago, PhotoGav said:

Much good advice posted already. Your question is "SCT or Refractor" for imaging? I would have to say, in general, a refractor is best for imaging DSO and an SCT for planetary. You can do the other with each, but at a compromise. Remember, the best scope is the one you enjoy using! Really you need a selection of scopes for all the different targets you want to view and image. I have a 71mm refractor, an 80mm refractor and an 8" SCT. I also have a very long shopping list of what I want to add to my arsenal! Top of that, after the observatory, is a long refractor, but that's because I like DSO imaging.

As Sara says, make sure you invest in a really good mount, HEQ5 at minimum.

For ease of learning to image DSOs, you can't go too wrong with a skywatcher 80ed and reducer to start you off. A 9.25" SCT would be a fine scope for planetary work, but I wouldn't start your DSO imaging journey with that, keep it for when you are more experienced.

Good luck and clear skies!

Hmmmm I do understand that one scope can't do everything hence your collection and sometimes I feel I have over researched this but then when I consider the hit to the bank account I realise the more research the better. I take on board the mount comments and considering I will be spending to me a significant amount of money I fully intend to future proof and therefore as suggested I will be looking at the NEQ6 PRO SynScan or the CGEM to handle potentially future heavier loads. I do wonder sometimes if I am a victim of marketing and missing other lesser used but equally well built makes or if Celestron and Sky Watcher are the leaders.

Either way I will not be able to purchase 2 scopes for a LONG time so need to consider what I will be wanting to do in a year or two and not regretting an earlier purchase. I'm always kind of optimistic and like a challenge so I wonder if a SCT for planetary observing and DSO will be the overall target, if only I could ask a future me in 10 years!!

[Mr Spock]

For mount you could do no better than the EQ6. My C9.25 is perfect on one, plus, stick an ED80 on it instead of the C9.25 and you have a great DSO imaging set up.

[Adaaam75]

10 hours ago, michael.h.f.wilkinson said:

I have bagged over 900 DSOs including 600 galaxies with an 8" SCT (so far), and don't understand why a 12" couldn't find many more than that. Most DSOs by far fit easily in the FOV of an SCT. A handful require wider fields.

 

I must say having now spent a good amount of time and consideration on the asteonomy tools website below i am happy that an 8"/9.25" SCT will deliver results that are not too big for the FOV

 

http://astronomy.tools/calculators/field_of_view/

[Mr Spock]

I have a Vixen LVW 42mm for my C9.25 which is as wide as you can go. The Pleiades are a tight squeeze but you can get them all in (just)

[Physopto]

Was that with a shoe horn 

Derek

[michael.h.f.wilkinson]

You can get the main stars in, but the outlying ones don't fit. M81 and M82 fit nicely in both the LVW42 and Nagler 31T5 Panzerfaust

[Adaaam75]

12 hours ago, Mr Spock said:

For mount you could do no better than the EQ6. My C9.25 is perfect on one, plus, stick an ED80 on it instead of the C9.25 and you have a great DSO imaging set up.

Would the EQ6 handle the weight of the 9.25 plus the potential weight of a guidescope, reducer, ccd and filter wheel comfortably without sgruggling?

 

[ollypenrice]

12 hours ago, Adaaam75 said:

 

Am I correct in saying that balancing Refractors can be more challenging when imaging but then i suppose due to their speed the imaging times are reduced compared to SCT's so long exposures wont be as common?

 

Thanks for your time in answering my queries!

 

Clear skies

 

No, there is nothing different about balancing a refractor than balancing anything else. Balancing isn't diffiult, don't worry about it.

As for exposure time, they can be shorter in a faster scope, though both Sara and I use 30 minute subs routinely in our fast refractors. Once you have gone beyond a couple of minutes you will certainly need to be guiding and, once doing that, if you can guide for 5 minutes you can guide for 30 assuming your polar alignment is correct.

Olly